1. Field
This invention relates to the field of sterilizers, and more particularly relates to apparatus and methods for steam sterilizers.
2. State of the Art
Tabletop sterilizers are small pressure vessels which are typically "unplumbed," i.e., the vapor sterilant is generated from a fixed amount of liquid sterilant placed in the electrically heated vessel and vaporized therein. The liquid is admitted to the sterilizer vessel by a metering valve or shot chamber or other means, i.e. by manually dumping a measured quantity of liquid into the vessel.
The quantity of added liquid, e.g., water, must be sufficient to maintain an atmosphere of saturated vapor sterilant at the desired sterilization temperature, irrespective of the type or quantity of material comprising the load to be processed.
When materials are sterilized, the hot vapor condenses on the cold materials during the heating cycle. The condensate may be retained in the surface of the materials and not be immediately returned to the heating means. Materials such as fabrics may retain a large quantity of condensate prior to attaining the sterilizing temperature.
When the condensate is not returned to the heater, additional liquid must be added to prevent the heating surfaces from drying out. Dry heater surfaces result in a very low heat transfer rate and prevent the materials from reaching sterilization conditions in a reasonable time.
If an excessive quantity of liquid is added to the sterilizer chamber, the heating period is also prolonged and additional energy is consumed. Furthermore, additional time is often required for removing moisture from the chamber and cooling the contents upon completion of the sterilization period.
A method and means for avoiding the abovementioned problems is needed.